PreBlocker is optional method module developers can implement in their module. They will be triggered before BeginBlock.

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PreBlocker​

There are two semantics around the new lifecycle method:
  • It runs before the BeginBlocker of all modules
  • It can modify consensus parameters in storage, and signal the caller through the return value.
When it returns ConsensusParamsChanged=true, the caller must refresh the consensus parameter in the deliver context: 
app.finalizeBlockState.ctx = app.finalizeBlockState.ctx.WithConsensusParams(app.GetConsensusParams())
The new ctx must be passed to all the other lifecycle methods.